# Boundary of nuclear material sample

## Main Question or Discussion Point

we know that the full life of radioactive sample is infinity.
and if we take one radioactive atom in the sample then it's full is measurable and short. it changes when when it emits sub atomic particles. which contradict each other.
we need to know more. the dimension of radioactive constant λ raises an other question.
here N=N0eλt the is on of e so what is the dimension of λ.

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Astronuc
Staff Emeritus
we know that the full life of radioactive sample is infinity.
and if we take one radioactive atom in the sample then it's full is measurable and short. it changes when when it emits sub atomic particles. which contradict each other.
we need to know more. the dimension of radioactive constant λ raises an other question.
here N=N0eλt the is on of e so what is the dimension of λ.
λ is the decay constant with units if inverse time. If time t is in seconds, then λ is sec-1.

N(t) = N0 exp(-λt)

The decay constant is also the inverse of the mean lifetime of the decaying species.

QuantumPion
Gold Member
we know that the full life of radioactive sample is infinity.
and if we take one radioactive atom in the sample then it's full is measurable and short. it changes when when it emits sub atomic particles. which contradict each other.
we need to know more. the dimension of radioactive constant λ raises an other question.
here N=N0eλt the is on of e so what is the dimension of λ.
There is no such thing as "full life", as such a quantity would depend on the sample size and not the properties of the material. But if you wanted to, you could define the "full-life" of a sample as the number of half lives required before you are left with a single atom. This "full-life" would not be infinity, in fact the value would be equal to approximately 79 half lives per mol of material (Na/2^79 ~= 1).

mfb
Mentor
Radioactive decay is a stochastic process (at least for all observers). You can give an expectation value (and a distribution function) for the time until all atoms decayed, but the time in an experiment will be random.